Lubricants



March 17, 1964 G GRAUE ETAL 3,125,519

` LUBRICANTS Filed Feb. 3, 1961 4 Sheets-Sheet 1 Fig. I

Jnvenor's March 17, 1964 G. GRAUE ETAL LUBRICANTS 4 Sheets-Sheet 2 Filed Feb. 3, 1961 m m., 1 I u( .w fo @Q 0 0 Iv l 5 5 QSQ/ .m ,w/ 1 .w s e n u .Ilvwbrlv .JMW gnu] o/O man 'l n. l 5 0 0 030.6 2 a P S U P g N.K.M 0 M. n n w m 9 .ll-I. |I\\ nl\\ 0 m 0 0 W M W M W N M W 0 7 5 5 4 lill uodfur Fig. 2

Jn venlors:

CaEOlG 4 Sheets-Sheet 3 illlwa m :in Q@ Il' .3. a. uw um 2.. QS Essi Q.

G. GRAUE ETAL LUBRICANTS l/ aan ai $2 sm March 17, 1964 Filed Feb. 5. 19e1 March 17, 1964 Filed Feb. s, 1961v G. GRAUE ETAL LUBRICANTS 4 Sheets-Sheet 4 Fig. 4 m

son

/" Kfs' United States Patent O 3,125,519 LUBRICANTS Georg Graue and Werner Lekerath, Homberg, Lower Rhine, Germany, assignors to Phoenix-Rheinrohr Aktiengesellschaft Vereinigte Huttenund Rohren- Werke, Dusseldorf, Germany l Filed Feb. 3, 1961, Ser. No. 86,932,

Claims priority, application Germany Feb. 9, 1960 3 Claims. (Cl. 252-11) Our copending U.S. application Serial No. 659,113, now Patent No. 2,990,610, relates to a heat-resistant water-soluble lubricant which contains a phosphate and a borate and is free from oil and fat. The lubricant pre-ferably consists of a melt of a mixture of an alkali metal tetraborate and the meta-, orthoor pyro-phosphate of an alkali metal, for example potassium or sodium. -lt is useful for lubricating metal work-pieces at high temperatures, for example when being hot-worked, and also for lubricating parts of machines and apparatus which are exposed to high temperatures when in operation. Mixtures of the aforesaid composition begin to soften at a relatively low temperature, for example 300 C. which is far below the melting point of their constituents and thus form eutectoid melts which, as the temperature increases, change from being highly viscous into a condition of lower viscosity, and are stable within a wide temperature range which extends up to 1,000 C. and above and act as lubricants. The mixture can be applied to the surface to be lubricated in the form of a melt, but it can also be applied as a dry powder or an aqueous solution, and in the latter case, the water not only serves as a solvent and carrier but also promotes a particularly rapid and uniform distribution of the lubricating agent. The mixtures in any of these forms can be applied to cold work and heated together with it or they can be applied to work `which has been previousely heated. Independently on the manner in which it is applied and of the time of its application, the mixture, when it is used inthe form of a solution and after the solvent has been evaporated, forms a eutectoid melt on the solid work-pieces. The melt first removes the scale from the wetted surface and then forms on the clean metal a coherent adhering iilm which is uniformly distributed over the surface and is resistant to high temperatures up to 1,000 C. and above.

The inventors have unexpectedly found in the course of further work on the development of the lubricant according to the parent patent that a lubricant having equally good properties is al-so produced if the alkali metal tetraborate in the aforesaid mixture is partly or even wholly replaced by an inorganic salt of an alkali metal or magnesium which forms eutectoid melts with alkali metal phosphates. This was quite unexpected since the eutectoid property of mixtures of salts is itself not a criterion for the lubricating elect of melts produced from them; moreover the mixtures used in accordance with the invention in the molten state are useful not only as lubricants but also for the removal of the layer of scale Patented Mar. 17, 1964 ice or oxide which is always present when air has access to highly-heated metal parts. It was hitherto assumed that the presence yof an alkali metal tetraborate (borax) was necessary for this purpose.

According to the present invention, in the lubricant according to the above mentioned copending application, the alkali metal tetraborate is partly or wholly replaced by an inorganic salt of an alkali metal or magnesium which forms a eutectoid melt with the alkali metal phosphate. It has been found by experience that sulphates and chlorides are particularly useful as such salts.

FIGS. 1 to 4 of the drawings show softening diagrams of different examples of mixtures which are included in the invention and in which the tetraborate is replaced as follows.

In FIG. 1 the alkali metal tetraborate is wholly replaced by sodium or potassium sulphate;

-ln FIG. 2 by magnesium sulphate, and in FIG. 3 by potassium chloride, whereas in FIG. 4 one-half of the sodium tetraborate is replaced by sodium sulphate.

It will be seen from all the figures that these mixtures form eutectoid melts which already begin to soften with suitable mixing ratios, for example 90% NaPO3-{10% Na2SO4, at about 300 C.; 38% Na2SO4-l-62% KPOB at about 440 C.; 22% KCl and 78% KPOZ at about 600 C.; 28% MgSO4+72% KPO3 at about 380 C.; and KPO3, 10% Na2B4O7 and 10% NaZSO,z at about 430 C., whereas with other compositions softening only begins at higher temperatures. By suitably selecting the constituents and by altering its percentage composition the lubricant can easily be adapted to suit the existing conditions at any time.

It has been found by experiment that the lubricating properties of the mixtures now proposed, in particular the alkali metal sulphate and phosphate mixture, are better than the mixtures according to the above mentioned copending application, particularly when working alloyed steels. The advantage obtained by the present invention, however, is chiefly that the sulphates and chloride of magnesium and of the alkali metals, especially sodium and potassium, are considerably less expensive than alkali metal tetraborates.

We claim:

l. A heat-resistant, oil and fat-free, water-soluble lubricant consisting essentially of a molecularly dehydrated alkali metal phosphate and an alkali metal tetraborate, said alkali metal tetraborate being at least partially replaced by a salt selected from the group consisting of the sulfates and chlorides of sodium, potassium and magnesium in an eutectoid mixture.

2. A lubricant as defined in claim l, wherein a sulfate is substituted for the tetraborate.

3. A lubricant as deined in claim 1, wherein a chloride is substituted for the tetraborate.

References Cited in the file of this patent UNITED STATES PATENTS 2,990,610 Luckerath et al. July 4, 1961 

1. A HEAT-RESISTANT, OIL, AND FAT-FREE, WATER-SOLUBLE LUBRICANT CONSISTING ESSENTIALLY OF A MOLECULARLY DEHYDRATED ALKALI METAL PHOSPHATE AND AN ALKALI METAL TETRABORATE, SAID ALKALI METAL TETRABORATE BEING AT LEAST PARTIALLY REPLACED BY A SALT SELECTED FROMTHE GROUP CONSISTING OF THE SULFATES AND CHLORIDES OF SODIUM, POTASSIUM AND MAGNESIUM IN AN EUTECTOID MIXTURE. 